COAL SCIENCE IMPACT ON COMBUSTION TECHNOLOGY

摘要

The focus of this presentation is on combustion as used primarily for steam raising in power generation. Contributions of coal science to technology development are highlighted by examples. Coal combustion technology has developed from mainly empirical beginnings to its present day sophistication by the gradual application of coal combustion science. Early examples are Werkmeister's (1931) ingenious laboratory study simulating the combustion on a Travelling Grate Stoker by his observations of the time resolved processes of combustion in a fixed bed, and Nusselt's (1924) classical studies of pulverized coal flame propagation and the diffusion controlled burning law for pulverized coal particles. These investigations provided valuable tools to designers to improve combustion on the travelling grate by the zoned distribution of the air along the grate,and the sizing of combustion space in pulverized coal fired boilers , respectively. The question of internal burning of small coal particles, with pore diffusion and surface reaction playing important roles in the overall rate of combustion, was raised by Essenhigh (1955) following of which evidence for chemical rate control was obtained by a number of investigators. The practical significance of these findings was their contribution to the developing art of furnace flame modeling. Examples include the use of kinetic data in the pioneering CFD simulation by Richter and Quack (1974) of Hein's (1971) pulverized anthracite flame data. As information on the yield and kinetics of devolatilization became available (Kobayashi et. al. 1976); Suuberg et.al.(1979), bituminous and lower rank coals could also be treated with more confidence by CFD modeling. (Smoot et.al. 1993; Fiveland et. al. 1993; Lockwood et.al. (1994). In a recent report of the International Energy Agency (1997) a comprehensive review is presented of the state of the art of pulverized coal combustion modeling. Modeling can guide experiments in research and development, and assist engineering design by providing information on trends and relative significance of design and operating variables upon performance. In turn, coal combustion modeling remains to be strongly dependant on coal science inputs on combustion, pollutant emissions, and coal mineral malter transformation during combustion.